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<br /> <br />. '-:-:"-~': <br /> <br />. ~., - <br />. .-."." <br />-,_.". <br /> <br />,~;;6':~,:;'~ <br /> <br />,-. ;~.," ".", <br /> <br /> <br />I <br /> <br /> <br />..,....',...'" <br />!;~i~i.~ <br /> <br />'...., . <br /> <br />~~i~~~5 <br />~!~ <br />~4~;] <br />~,g~{ <br />~_..~ <br />i~~;{~ <br />;~~ <br />/:~~~ <br />8';,~ <br /> <br />:'~.:-- - . <br /> <br />.. <br /> <br />",;':'~.,;;'4 <br /> <br />:~~~~f~ <br />......~'..,~~'. <br />~~~f~ <br /> <br />;-,' <br /> <br />"'r,"~ <br /> <br />filY'" <br /><. <br />:o::~~, <br />~.,.-.b <br />=;~i{:; <br /> <br />i'. <br /> <br />. . <br /> <br />G'.':' <br />.. <br /> <br />0,,",' <br />_,_:,,'h~ <br />.:~. <br /> <br />All but the upper three square miles of the Sheep Draw basin has the <br /> <br />Olney-Kim-Otero soil association. An infiltration rate of 0.8 inch~/hour <br /> <br />was selected as being representative o~ the ranges given above. A value of <br /> <br />0.2 inch was used for detention storage on pervious and impervious areas. <br /> <br />d. Other Model Parameters. The SWMM model of the Sheep Draw basin <br /> <br />contains 107 subcatchments, 80 streams, 13 road structures, and 4 dams. The <br /> <br />percent imperviousness of each sub catchment was estimated for existing, <br /> <br />projected urbanized, and fully urbanized conditions. Table 3 lists the percent <br /> <br />imperviousness for each land use that was considered in the model. <br /> <br />TABLE 3 <br /> <br />PERCENT IMPERVIOUSNESS FOR LAND USES <br />IN SHEEP DRAW BASIN <br /> <br />Land Use <br /> <br />Impervious Area <br />% <br />90 <br />40 <br />5 <br /> <br />Commercial <br />Medium Density Residential <br />Agricultural <br /> <br />Each stage of development (existing, projected urbanized, and fully urbanized) <br />., <br />was modeled with and without the dams in place. Since the reservoirs are used <br /> <br />for irrigation, it is not known if they will remain intact as the basin urbanizes. <br /> <br />5. DISCHARGE PROBABILITY. <br /> <br />a. General. The various discharge probability profiles developed with the <br /> <br />SWMM model for the Sheep Draw basin are discussed in the following paragraphs. <br /> <br />b. Existing Conditions. The 2-, 5-, 10-, 50-, 100-, and SOD-year discharges <br /> <br />for existing conditions with and without dams are presented in Tables 4 and 5 <br /> <br />and are shown on attachments 3 and 4 as discharge profiles. Attachment 5 is a dis- <br /> <br />charge profile that indicates the effects of the road structures and dams on the <br /> <br />100-year existing event. <br /> <br />4 <br />